Phantom limb pain happens to people who have had limb amputations. They continue to feel the presence of the amputated part, and especially, pain in that area. Though the effect has been known for a long time, it is poorly understood. Now, based on a treatment that uses machine learning and augmented reality, a researcher from Sweden has a hypothesis regarding the effect. The proposal is that neural circuitry, after an amputation loses its primary role and becomes entangled with other neural networks which are responsible for pain perception. The coincidental firing of these neurons with the ones involved in pain perception is what, according to him, causes the pain.